Comparison of the action of the 5-HT2 antagonists amperozide and trazodone on preference for alcohol in rats

Evaluation of multitarget drugs on the expression of cocaine-induced locomotor sensitization in male rats: A comparative study

Purpose

- Cocaine use disorder (CUD) is a complex disease. Several studies have shown the efficacy of multitarget drugs used to treat CUD. Here we compare the efficacy of mirtazapine (MIR), pindolol (PIN), fluoxetine (FLX), risperidone (RIS), trazodone (TRZ), ziprasidone (ZPR), ondansetron (OND), yohimbine (YOH), or prazosin (PRZ), to reduce long-term cocaine-induced locomotor activity and the expression of cocaine-induced locomotor sensitization in rats.

Methods

- The study consists of four experiments, which were divided into four experimental phases. Induction (10 days), cocaine withdrawal (30 days), expression (10 days), and post-expression phase (10 days). Male Wistar rats were daily dosed with cocaine (10 mg/kg; i.p.) during the induction and post-expression phases. During drug withdrawal, the MIR, PIN, FLX, RIS, TRZ, ZPR, OND, YOH, or PRZ were administered 30 min before saline. In the expression, the multitarget drugs were administered 30 min before cocaine. After each administration, locomotor activity for each animal was recorded for 30 min.During the agonism phase, in experiment four, 8-OH-DPAT, DOI, CP-809-101, SR-57227A, or clonidine (CLO) was administered 30 min before MIR and 60 min before cocaine. After each administration, locomotor activity for each animal was recorded for 30 min.

Results

-MIR, FLX, RIS, ZPR, OND, or PRZ attenuated the cocaine-induced locomotor activity and cocaine locomotor sensitization. PIN, TRZ, and YOH failed to decrease cocaine locomotor sensitization. At the optimal doses used, PIN, FLX, RIS, TRZ, ZPR, OND, YOH, or PRZ failed to attenuate long-term cocaine locomotor activation. MIR generated a decrease in cocaine-induced locomotor activity of greater magnitude and duration than the other multitarget drugs evaluated.

Conclusion

- At the optimal doses of multitarget drugs evaluated, MIR was the multitarget drug that showed the greatest long-term cocaine-induced behavior effects compared to other multitarget drugs.

An assessment of the utilization of the preclinical rodent model literature in clinical trials of putative therapeutics for the treatment of alcohol use disorders

OBJECTIVE

Rodent models of Alcohol Use Disorders (AUD) are used extensively by preclinical researchers to develop new therapeutics for the treatment of AUD. Although these models play an important role in the development of novel, targeted therapeutics, their role in bringing therapeutics to clinical trials is unclear, as off-label use of existing medications not approved for the treatment of AUD is commonly seen in the clinic and clinical trials.

METHOD

In the current study, we used the Clinicaltrials.gov database to obtain a list of drugs that have been tested for efficacy in a clinical trial between 1997 and 2017. We then conducted a set of literature searches to determine which of the 98 unique drugs we identified had shown efficacy in a rodent model of an AUD prior to being tested in a clinical trial.

RESULTS

We found that slightly less than half of the drugs tested in clinical trials (48%) had shown prior efficacy in any rodent model of an AUD, while the remaining 52% of drugs were used off-label, or in some cases, following non-published studies.

CONCLUSION

This study raises the question of how clinical researchers incorporate results from preclinical studies in the decision to bring a drug to a clinical trial. Our results underscore the need for ongoing communication among preclinical and clinical researchers.

Cocaine-conditioned locomotion in dopamine transporter, norepinephrine transporter and 5-HT transporter knockout mice

The behavioral effects of cocaine are affected by gene knockout (KO) of the dopamine transporter (DAT), the serotonin transporter (SERT) and the norepinephrine transporter (NET). The relative involvement of each of these transporters varies depending on the particular behavioral response to cocaine considered, as well as on other factors such as genetic background of the subjects. Interestingly, the effects of these gene knockouts on cocaine-induced locomotion are quite different from those on reward assessed in the conditioned place preference paradigm. To further explore the role of these genes in the rewarding effects of cocaine, the ability of five daily injections of cocaine to induce conditioned locomotion was assessed in DAT, SERT and NET KO mice. Cocaine increased locomotor activity acutely during the initial conditioning session in SERT KO and NET KO, but not DAT KO, mice. Surprisingly, locomotor responses in the cocaine-paired subjects diminished over the five conditioning sessions in SERT KO mice, while locomotor responses increased in DAT KO mice, despite the fact that they did not demonstrate any initial locomotor responses to cocaine. Cocaine-induced locomotion was unchanged over the course of conditioning in NET KO mice. In the post-conditioning assessment, conditioned locomotion was not observed in DAT KO mice, and was reduced in SERT KO and NET KO mice. These data reaffirm the central role of dopamine and DAT in the behavioral effects of cocaine. Furthermore, they emphasize the polygenic basis of cocaine-mediated behavior and the non-unitary nature of drug reward mechanisms, particularly in the context of previous studies that have shown normal cocaine-conditioned place preference in DAT KO mice.

Effects of cocaine and putative atypical antipsychotics on rat social behavior: an ethopharmacological study

The effects of cocaine, amperozide, clozapine, olanzapine and cocaine/atypical antipsychotic combinations on aggression, affiliation and defensive behaviors was examined. Acute cocaine (30.0 mg/kg) decreased basal aggression and affiliation yet increased basal defense. Amperozide (1.0, 3.0 and 5.0 mg/kg) decreased basal aggression, affiliation and defense had no effect on the cocaine-induced decrease in affiliation, and accentuated the cocaine-induced decrease in aggression. Near basal levels of defense were observed for animals treated with either amperozide, clozapine (3.0 and 10.0 mg/kg but not 30.0 mg/kg) or olanzapine followed by cocaine. Clozapine (3.0, 10.0 and 30.0 mg/kg) decreased basal aggression and affiliation. Clozapine (30.0 mg/kg but not 3.0 or 10.0 mg/kg) decreased basal defense. Clozapine attenuated the cocaine-induced decrease in aggression. Although 3.0 and 10.0 mg/kg clozapine attenuated the cocaine-induced decrease in affiliation, 30.0 mg/kg clozapine accentuated this cocaine-induced effect. Olanzapine (1.0, 3.0 and 10.0 mg/kg) decreased basal aggression, affiliation and defense. Olanzapine had no effect on the cocaine-induced decrease in aggression. Olanzapine (3.0 mg/kg but not 1.0 or 10.0 mg/kg) attenuated the cocaine-induced decrease in affiliation. Thus, acute cocaine administration had an antiaggressive effect, suppressed affiliative behavior and enhanced defensive behavior. Amperozide, clozapine and olanzapine have anticonflict and anxiolytic effects, as well as potent and specific antiaggressive effects.

Amperozide influences feeding independently of 5-HT2A receptor antagonism

Amperozide has been biochemically classified as a selective 5-HT2A (serotonin type 2A) receptor antagonist. However, research on the behavioral effects of amperozide suggests the possibility of other mechanisms. The present study in the male rat is an investigation of the effect of amperozide on feeding, a behavior which can be inhibited by 5-HT2A agonists such as 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Experiments revealed that amperozide acted to inhibit feeding behavior both when administered alone and when administered in combination with DOI. These results are inconsistent with 5-HT2A receptor antagonism by amperozide. Further experiments suggested that amperozide may be acting via alpha 2-adrenergic or 5-HT1A receptors to inhibit feeding. These studies imply that amperozide's selective 5-HT2A antagonistic activity is behaviorally specific.

The effects of amperozide on cocaine-induced social withdrawal in rats

Cocaine decreases social interactions in both humans and animals, but it is not known whether the drugged animal withdraws from an undrugged conspecific, the undrugged conspecific avoids the drugged animal, or a combination of these two factors occurs. In the first experiment, the source of cocaine-induced social withdrawal was determined using a tether paradigm, in which the movement of one of the rats was restricted to one half of the observation chamber, such that the freely moving rat had the option of escaping social interactions. There were decreases in social interactions in the condition in which both rats were freely moving, and in the condition in which the undrugged rat was tethered, but not when the drugged rat was tethered and could not escape social contact. A second experiment was conducted to test the efficacy of the potent serotonin receptor antagonist, amperozide, in attenuating cocaine-induced social withdrawal using the condition in which the drugged rat was freely moving. Either amperozide (1.0, 3.0, and 5.0 mg/kg) or saline vehicle was injected into rats 1 h before receiving a 30.0 mg/kg cocaine dose. Cocaine decreased social interactions. Amperozide restored social interactions to near control levels and elevated social interactions in the animals treated with saline vehicle.

The cardiovascular effects of amperozide: interactions with cocaine

Amperozide is a 5-HT2A receptor antagonist that significantly reduces the acquisition and expression, by rats, of a cocaine conditioned place preference. In order to rule out the possibility that amperozide affects a cocaine conditioned place preference due to effects on blood pressure or heart rate, the cardiovascular effects of amperozide were investigated. Alternating cumulative doses of amperozide (0.5, 1.0, 1.5 and 2.5 mg kg(-1)) or saline and phenylephrine (8 microg kg(-1)) were administered through the femoral vein of awake freely-moving Sprague-Dawley rats and blood pressure and heart rate were recorded from the femoral artery. A single dose of cocaine (5.0 mg kg(-1)) was administered after all the amperozide or saline doses were given. Amperozide (0.5, 1.0, 1.5 and 2.5 mg kg(-1)) did not have any significant effect on blood pressure compared to the saline control treatment to the same animals. However, 0.5 mg kg(-1) amperozide significantly decreased heart rate at 5 and 10 min. after administration. but higher doses did not further depress heart rate. Amperozide did not affect the increased blood pressure and decreased heart rate caused by phenylephrine. an alpha1-adrenoceptor agonist. In addition, amperozide did not affect the cardiovascular response to an intravenous dose of 5.0 mg kg(-1) cocaine. These results suggest that amperozide does not cause direct cardiovascular effects. The mechanism by which the lowest dose of amperozide caused a decrease in heart rate is unknown. Amperozide affects neither alpha-adrenoceptor mediated vasoconstriction nor the increased sympathetic activity caused by the peripheral and central effects of cocaine. The significance of these results, in terms of locomotor activity and the cocaine conditioned place preference paradigm, is discussed.

Nefazodone attenuates the behavioral and neurochemical effects of ethanol

This study evaluated the influence of nefazodone, a combined 5-HT2A receptor antagonist and 5-HT reuptake inhibitor, on the behavioral and neurochemical effects of ethanol in nonselected male Wistar rats. In microdialysis experiments, ethanol (2.5 g/kg, i.p.) increased extracellular accumbal dopamine levels by 36% (p = 0.0073) compared to baseline levels, and elevated the maximal DOPAC and HVA levels by 26% (p = 0.0093) and 52% (p = 0.0010), respectively, Nefazodone (50 mg/kg, s.c.) per se increased accumbal dopamine levels by 28% (p = 0.0199) but, when injected 40 min before ethanol, reduced the ethanol-induced elevation of accumbal dopamine overflow (p = 0.0132) and decreased the ethanol-induced HVA levels (p = 0.0159). In an ethanol(6% v/v)/water free-choice paradigm, nefazodone (50 mg/kg, s.c.) decreased ethanol intake by 51% (p = 0.0251) and preference by 22% (p = 0.0251) in high- but not low-preferring rats from a nonselected Wistar strain. These results show that nefazodone modulates the mesolimbic dopamine system in a dopamine activity-dependent manner, and influences the neurochemical and behavioral effects of ethanol in the rat.

Differential efficacy of serotonergic drugs FG5974, FG5893, and amperozide in reducing alcohol drinking in P rats

Amperozide (FG5606), a 5-HT2 receptor antagonist, is well known to suppress alcohol consumption in different rat models of drinking. The present study compared the efficacy of three drugs, FG5974, FG5893, and amperozide, which have differential affinities for 5-HT1A and 5-HT2A receptors, on alcohol drinking in the genetic alcohol-preferring (P) rat. After preference for alcohol vs. water was determined over 10 days when concentrations of alcohol were increased from 3% to 30%, the maximal concentration of alcohol preferred by each animal was selected for drug testing. A 4-day predrug preference test was followed by SC injection of the saline control vehicle or doses of 1.0 and 2.5 mg/kg FG5974, FG5893, or amperozide given at 1600 and 2200 h for 4 days. Alcohol preference testing concluded with a final 4-day interval. A total daily dose of 5.0 mg/kg FG5974 reduced absolute g/kg intake of alcohol and proportional intakes of the P rats significantly; the lower dose of FG5974 also reduced alcohol drinking significantly following treatment. The mixed 5-HT1A agonist/5-HT2A antagonist, FG5893, which suppresses drinking in cyanamide-treated rats, was without effect on alcohol ingested by the P rats. However, amperozide caused a dose-dependent decline in both absolute intakes and proportion of alcohol that was more intense than that of FG5974. The control vehicle failed to alter alcohol drinking and, like the FG compounds, did not affect food intake or body weight. Although the inhibition of alcohol drinking by amperozide corresponds precisely with previous findings, the effect of FG5974 contrasts to results obtained with a structurally analogous drug FG5893. Thus, the genetic strain of rat as well as the nature of the chemical characteristics of a 5-HT agonist/antagonist will determine the differential efficacy of a drug in influencing the volitional drinking of alcohol.

Synthesis of dopamine and 5-HT in anatomical regions of the rat's brain is unaffected by sustained infusion of amperozide

The 5-HT2A antagonist, amperozide, is considered to be a potentially useful drug for the treatment of substance abuse. The effects of this drug on the Sprague-Dawley rat were examined on the synthesis of dopamine and serotonin (5-HT) as well as on the intakes of food and water and the level of body weight. Amperozide was delivered subcutaneously by osmotic minipump in doses of 2.5 mg/kg or 5.0 mg/kg per day for 7 days. After injection of 100 mg/kg NSD-1015, each brain was dissected post mortem into midbrain, pons, hypothalamus, septum, nucleus accumbens, striatum, frontal cortex and the hippocampus. Neither concentration of amperozide altered the synthesis of dopamine or 5-HT, as measured in terms of the formation of 1-3,4-dihydroxyphenylalanine (L-DOPA) and 5-hydroxytryptophan (5-HTP), respectively, in any of the 8 brain regions analyzed. Both doses of amperozide reduced food intake by 20% within 24 hr after implantation of the pumps, but feeding resumed postoperatively at the control level within 48 hr. Amperozide affected neither the intake of water nor the level of body weight. The lack of effect on the synthesis of dopamine and 5-HT and the absence of side effects on the intakes of food and water suggest that amperozide may be a specific agent for suppressing alcohol drinking.

Volitional consumption of ethanol by fawn-hooded rats: effects of alternative solutions and drug treatments

Behavioral and neurochemical measures of brain 5-hydroxytryptamine (5-HT) function in the Fawn-Hooded rat are abnormal relative to outbred strains of rats. Fawn-Hooded rats freely drink large amounts of 10% ethanol in the presence of water and have been proposed to be an animal model for studies related to alcoholism. In this study, Fawn-Hooded rats were given solutions of ethanol increasing in concentration from 3% to 30% (w/v in tap water) over 10 days with tap water in a second drinking tube and a third tube left empty. The solutions of ethanol that produced maximal drinking with a preference (ml ethanol/ml total fluid) near 50% ranged from 5% to 13%, which became the fixed individual concentrations for each rat. After a 5-day baseline period the rats were offered a solution in the third drinking tube of either 0.5% aspartame or chocolate Ultra SlimFast (diluted with water 2:1). The chocolate drink, but not aspartame, significantly reduced the consumption of alcohol by 73%. For the drug experiments, the rats were given successive 4-day periods of: baseline drinking; drug or saline injections b.i.d.; and a posttreatment period. Neither ipsapirone, a 5-HT1a partial agonist, nor naltrexone injected inhibited the intakes of ethanol solutions. Treatment with 2.5 mg/kg of amperozide, a 5-HT2 antagonist, decreased the consumption of ethanol by 38%, but also caused a decrease in consumption of food. These results show a pattern of drinking of increasing concentrations of ethanol different than other strains of rats.(ABSTRACT TRUNCATED AT 250 WORDS)